1. Field of the Invention
This invention relates to a magnetic disk cartridge containing a thin magnetic disk of small diameter which is rotated for image recording and reproduction thereon. More particularly, this invention relates to a structure for adhering the magnetic disk to a center core.
2. Description of the Prior Art
Recording media comprising floppy disks which consist of a base of flexible polyester sheet or the like which is coated on both sides with a layer of magnetic material in which information is recorded digitally by means of a magnetic head have been developed which are widely used as recording media for computers because of their handling ease and convenience and low cost. In recent years the so-called microfloppy disk has started to be introduced commercially. For improved handling convenience, reliability and resistance to dust and dirt, the microfloppy disk is smaller and is housed in a hard case of plastic resin provided with a magnetic head access window which has a shutter. There has been proposed a still camera using such floppy disks as image recording media to utilize the above adantages of the floppy disk and the advantage of reusability of the recording media provided by magnetic recording and not possessed by silver-based photographic film. The magnetic disks for use in such a still camera, which is about the size of a conventional 35 mm camera, are even smaller and thinner and are housed in a magnetic disk cartridge which also has been made smaller and of a hard material (and which for brevity will from now on be referred to herein simply as "cartridge") in which the media is rotated at high speed for the recording and reproduction.
In order to record large quantities of information on the small magnetic disks employed in these small cartridges, recording densities have become extremely high, so that the slightest deformation or displacement of the disk produces spacing loss, being poor or uneven contact between the magnetic read/write head and the disk, producing uneven electromagnetic conversion readout output and distortion of the information recording/reproduction, in all likelihood making it difficult to achieve good recording/reproduction. Also, unlike the conventional floppy disk wherein a central locating hole is utilized in the support of the disk by two mechanical members of the disk drive which hold the disk therebetween, with the cartridge the disk is provided with a center core into which a shaft is fitted from one side to provide the rotation. In order to transmit the rotation to the disk it is necesssary that the disk and core be fixed together. Various tecniques are used to prevent deformation to the disk during this fixing process. An example of one such method is shown in FIG. 3, in which a floored, cylindrical center core 1 which has a hole 1a in the center of the floor and a flange 1b around its upper periphery is adhered to a magnetic disk 2 which has a center hole 2a by means of a ring-shaped double-sided adhesive member 3 interposed between the lower surface of the flange 1b and the upper edge of the hole 2a, and assembly is by the insertion of the cylindrical portion 1c of the center core 1 into the inner hole 2a. This method allows the assembly to be carried out automatically by means of robots. However, this method does require the use of an adhesive member, such as the double-sided adhesive tape 3, and the pressure at the time of the adhesion produces non-uniformity in the thickness of the adhesive tape, causing wrinkling of the disk, and as to the precision of the concentricity with which the adhesive tape 3 is automatically fixed to the lower surface of the flange 1b of the center core 1 and around the periphery of the inner hole 2a of the disk 2, it is easy for the adhesive tape to be adhered out of true with respect to the center core or the disk prior to the completion of final assembly, and because the positional correction of the disk or center core is difficult, this has given rise to problems of cost and productivity.